Bis(catecholato)silanes: assessing, rationalizing and increasing silicon's Lewis superacidity

Abstract

The Lewis acidity of bis(catecholato)silanes is scaled and rationalized. Perbromination of the catechols provides the strongest silicon Lewis superacid.

An Extensive Set of Accurate Fluoride Ion Affinities for p‐Block Element Lewis Acids and Basic Design Principles for Strong Fluoride Ion Acceptors

“…The OC 6 F 5 ligand offers a low‐lying π ‐system for the free electron pair to delocalize also in the opposite direction. For group 14 species, it is the π ‐electron density that matters more, in line with previous findings for bis(catecholato)silanes . For group 13 and 15 elements, especially for the most electronegative P and B, the σ‐electron‐withdrawing effect gains more weight, and the OC(CF 3 ) 3 becomes more effective.…”

[Si(O2C6F4)2]14: Self‐Assembly of a Giant Perfluorinated Macrocyclic Host by Low‐Barrier Si−O Bond Metathesis

“…[13d] The pentacoordinate transition state is stabilized by the high Lewis acidity of the monomers, facilitating rapid chain-growth and exchange. [14] Hence, all spectroscopic and theoretical findings strongly suggested different oligomeric fragments of composition [Si(cat F ) 2 ] n under the approach to equilibrium at the given conditions (Figure 1). Storing the solutions of the sublimate in various solvents led to the crystallization of a compound 1, cocrystallized with disordered solvent molecules.…”

“…The acetonitrile adduct of bis(perfluorocatecholato)silane, Si(cat F ) 2 •(CH 3 CN) 2 , [14] was sublimed at 250 8C under 5.0 10 À2 mbar dynamic vacuum ( Figure 1). Under such conditions, the coordinated CH 3 CN dissociated first, as was observed by IR-spectroscopy, [14b] followed by the sublimation of putative, monomeric Si(cat F ) 2 .…”

“…The rigid cavity is either filled with solvent molecules or capable of uptaking two o-dodecacarboranes. As the silicon centers in the macrocycle remain Lewis acidic, [14] the compound potentially leverages new forms of molecular recognition or nanoconfined catalysis by action as polytopic Lewis acid. The low barrier Si-O/Si-O exchange sheds new light on our understanding of silicon ester dynamic covalent chemistry and the unique role of natural catechols in silica biomineralization.…”

Reversible Silylium Transfer between P‐H and Si‐H Donors

“…The electrophilic activation of Si−H bonds by Lewis acids (LAs) is increasingly exploited as a fundamental step in a range of catalytic reactions of silanes, [1, 2] a development that has been complemented by an explosion of interest in the discovery of new main group LAs [3] . This exciting class of compounds now extends well beyond neutral group 13 reagents [4] to include low‐coordinate, cationic boron and aluminum species [5] and diverse new structures based on elements from groups 14, [2c,h, 6] 15, [2e, 7] and 16 [8] . While the LAs themselves are of fundamental interest and importance for the variety of electronic structures that permit acceptor behavior, [9] the specific role of silane‐LA interactions in catalysis has also come under increasing scrutiny (Scheme 1).…”